Microbiology Chapter 8

Incubation

After media are inoculated, they must be incubated (i.e., they must be placed into a chamber [called an incubator] that contains the appropriate atmosphere and moisture level and is set to maintain the appropriate temperature).

Antiseptics

Antimicrobial chemical agents that can safely be applied to skin

Importance of using "aseptic technique"

Aseptic technique is practiced in the microbiology laboratory to prevent infection of individuals and contamination of the work environment, clinical specimens, and cultures.

Examples of enriched medium (2)

Blood agar & Chocolate agar

How much water are cells composed of?

Cells are composed of between 70% and 95% water.

Disinfectants

Chemicals used to disinfect inanimate objects, such as bedside equipment and operating rooms

Dry Heat

Dry-heat baking in a thermostatically controlled oven provides effective sterilization of metals, glassware, some powders, oils, and waxes. These items must be baked at 160°C to 165°C for 2 hours or at 170°C to 180°C for 1 hour.

Cytopathic effect (CPE)

If present, a given virus will cause specific morphologic alterations to the cells.

Plasmolysis

If the cell is a bacterial cell, having a rigid cell wall, the cell does not shrink. Instead, the cell membrane and cytoplasm shrink away from the cell wall; also inhibits bacterial cell growth and multiplication

Crenation

If the cell is a human cell, such as a red blood cell (erythrocyte), the loss of water causes the cell to shrink; this shrinkage is called

Plasmoptysis.

If the pressure becomes so great that the cell ruptures, the escape of cytoplasm from the cell is referred to

Places where it is desirable to inhibit growth of microbes...and why

In hospitals, nursing homes, and other healthcare institutions, for example, it is necessary to inhibit the growth of pathogens so that they will not infect patients, staff members, or visitors. Other environments in which it is necessary or desirable to inhibit microbial growth include food and beverage processing plants, restaurants, kitchens, and bathrooms.

What are the 2 types of culture mediums?

Liquid (broth) Solid (Slant)

Fastidious

Microorganisms that are difficult to grow in the laboratory

Halophiles.

Microorganisms that prefer salty environments

Psychroduric organisms

Microorganisms that prefer warmer temperatures, but can tolerate or endure very cold temperatures and can be preserved in the frozen state; like bread molds in the fridge

Gaseous Atmosphere

Microorganisms vary with respect to the type of gaseous atmosphere that they require. Like obligate aerobes/obligate anaerobes

What happens to microogranisms in the cold?

Most microorganisms are not killed by cold temperatures and freezing, but their metabolic activities are slowed, greatly inhibiting their growth

Binary fission on solid medium

On solid medium, binary fission continues through many generations until a colony is produced

Which microorganisms are killed when exposed to the sun?

Only the ones exposed to direct sunlight

Haloduric organisms

Organisms that do not prefer to live in salty environments but are capable of surviving there (such as Staphylococcus aureus)

Osmotic Pressure and Salinity

Osmotic pressure is the pressure that is exerted on a cell membrane by solutions both inside and outside the cell. HIGH to LOW Halophilic, halo referring to "salt" and philic meaning "to love." Microbes that live in the ocean, such as V. cholerae (mentioned earlier) and other Vibrio species, are halophilic. Organisms that do not prefer to live in salty environments but are capable of surviving there (such as Staphylococcus aureus) are referred to as haloduric organisms.

Barometric Pressure

Piezophiles (formerly called barophiles) live in environments where there is high barometric pressure, such as at the bottom of the ocean.

viable plate count

used to determine the number of viable bacteria in a liquid sample, such as milk, water, ground food diluted in water, or a broth culture

aseptic techniques

used to eliminate and exclude pathogens

Examples of microorganisms that will not grow on artificial media

Treponema pallidum (the causative agent of syphilis) and Mycobacterium leprae (the causative agent of leprosy).

True or False...It is possible to inhibit growth of microorganisms by altering the atmosphere in which they are located.

True

True or False..Chemical disinfection refers to the use of chemical agents to inhibit the growth of pathogens, either temporarily or permanently.

True

Algicidal agents

used to kill algae in swimming pools and hot tubs.

binary fission

When each bacterial cell reaches its optimum size, it divides by binary fission (bi meaning "two") into two daughter cells (i.e., each bacterium simply splits in half to become two identical cells).

Hypertonic

When the concentration of solutes in the environment outside of a cell is greater than the concentration of solutes inside the cell

Isotonic

When the concentration of solutes outside a cell equals the concentration of solutes inside the cell

Hypotonic

When the concentration of solutes outside a cell is less than the concentration of solutes inside the cell

Microbistatic agent

a drug or chemical that inhibits reproduction of microorganisms, but does not necessarily kill them

Autoclave

a large metal pressure cooker that uses steam under pressure to completely destroy all microbial life

Lyophilization

a process that combines dehydration (drying) and freezing; a good method of preserving microorganisms for future use.

Selective medium

has added inhibitors that discourage the growth of certain organisms without inhibiting growth of the organism being sought used to discourage the growth of certain organisms without inhibiting growth of the organism being sought.

thermal death point (TDP)

the lowest temperature that will kill all the organisms in a standardized pure culture within a specified period

Osmotic pressure

the pressure that is exerted on a cell membrane by solutions both inside and outside the cell.

Stationary phase

the rate of division slows, such that the number of bacteria that are dividing equals the number that are dying

Sanitization

the reduction of microbial populations to levels considered safe by public health standards, such as those applied to restaurants.

Acidophiles

thrive in highly acidic environments, such as those created by the production of sulfurous gases in hydrothermal vents and hot springs as well as in the debris produced from coal mining; prefer a pH of 2 to 5 Ex: FUNGI

Why the growth of microbes in vitro is important

to isolate microorganisms from clinical specimens and grow them on culture media so they can then gather information that will enable identification of any pathogens that are present.

Sterilization

the destruction or elimination of all microbes.

thermal death time (TDT)

the length of time necessary to sterilize a pure culture at a specified temperature.

Generation time

The time it takes for one cell to become two cells by binary fission

Factors that affect Microbial Growth

-Availability of Nutrients -Moisture -Temperature -pH -Osmotic Pressure and Salinity -Barometric Pressure -Gaseous Atmosphere

What are the four phases of the growth curve?

-lag phase -logarithmic growth phase(log) -stationary phase -death phase

Hemolysis

. If the cell is a human cell, such as an erythrocyte, the increased water within the cell causes the cell to swell. If sufficient water enters, the cell will burst (lyse). In the case of erythrocytes, this bursting is called hemolysis

Three types of incubators are used in a clinical microbiology laboratory

1- Carbon dioxide 2- non-carbon dioxide 3- An anaerobic incubator

Halophilic

Halo referring to "salt" and philic meaning "to love

Moist heat

Heat applied in the presence of moisture, as in boiling or steaming, is faster and more effective than dry heat, and can be accomplished at a lower temperature; thus, it is less destructive to many materials that otherwise would be damaged at higher temperatures

What is heat used for?

Heat is the most common type of sterilization for inanimate objects able to withstand high temperatures.

Lag phase

The first phase of the growth curve during which the bacteria absorb nutrients, synthesize enzymes, and prepare for cell division. The bacteria do not increase in number during the lag phase.

Artificial media/ synthetic media

The media (sing., medium) that are used in microbiology laboratories to culture bacteria

Death phase/ Decline phase

The microorganisms then die at a rapid rate

Ultrasonic waves

The sound waves mechanically dislodge organic debris on instruments and glassware.

Moisture

all living organisms require water to carry out their normal metabolic process

Differential medium

allows one to readily differentiate among the various types of organisms that are growing on the medium.

How do bacteria multiply?

by binary fission

In virology labs what are cell cultures primarily used for?

cell cultures are primarily used for the propagation of viruses. Because a given virus can only attach to and infect cells that bear appropriate cell receptors, it is necessary to maintain several different types of cell lines in the virology laboratory.

Viricidal agents

destroy viruses

What is a Spectrophotometer used for?

determine the total number of cells using a beam of light (that passes through the liquid)---if no bacteria is present, the liquid is clear. when turbidity increases so does the number of bacteria

population growth curve

determines the growing of a pure culture of the organism in a liquid medium at a constant temperature.

Temperature

every microorganism has an optimal, a minimum, and a maximum growth temperature

Logarithmic growth phase (log phase)

exponential growth phase; In the log phase, the bacteria multiply so rapidly that the number of organisms doubles with each generation time

suffix "-static"

inhibits the microorganism's growth and reproduction

Inoculation of a liquid medium

involves adding a portion of the specimen to the medium.

Disinfection

involves the elimination of most or all pathogens (except bacterial spores) from nonliving objects.

Inoculation of a solid/ plated medium

involves the use of a sterile inoculating loop to apply a portion of the specimen to the surface of the medium; a process commonly referred to as streaking

Enriched medium

is a broth or solid medium containing a rich supply of special nutrients that promotes the growth of fastidious organisms.

Bacterial colony

is a mound or pile of bacteria containing millions of cells.

Chemically defined medium

is one in which all the ingredients are known; this is because the medium was prepared in the laboratory by adding a certain number of grams of each of the components (e.g., carbohydrates, amino acids, salts)

Complex medium

is one in which the exact contents are not known. Ex: contain ground up or digested extracts from animal organs (e.g., hearts, livers, brains), fish, yeasts, and plants, which provide the necessary nutrients, vitamins, and minerals

Tuberculocidal agents

kill M. tuberculosis

Pseudomonicidal agents

kill Pseudomonas species,

Bactericidal agents

kill bacteria (not always bacterial endospores)

Fungicidal agents

kill fungi, including fungal spores

suffix "-cidal"

kill organisms

Availability of Nutrients

many nutrients are energy sources, organisms will obtain energy from these chemicals by breaking chemical bonds (Nutrients also serve as sources of carbon, oxygen, hydrogen, nitrogen, phosphorus and sulfur

Asepsis

means the absence of pathogens

Mesophiles

microbes that grow best at moderate temperatures

Bacteriostatic agent

one that specifically inhibits the metabolism and reproduction of bacteria

Psychrophiles

organisms that "love" cold temperatures

Thermophiles

organisms that "love" high temperatures

Antisepsis

prevention of infection.

bacterial growth

refers to an increase in the number of organisms rather than an increase in their size

pH

refers to the hydrogen ion concentration of a solution and, thus, the acidity or alkalinity of the solution (Acidophiles prefer acidic environments, whereas alkailphiles prefer environments that are alkaline)

Sepsis

refers to the presence of pathogens in blood or tissues

Sporicidal agents

required to kill bacterial endospores

Antiseptics

solutions used to disinfect skin and other living tissues.

What are two factors that determine effectiveness?

temperature and time